This relates to resinous coupled block copolymers.
It is known to produce block copolymers by the sequential addition of monomers such as styrene and butadiene. It is further known to produce a completely different class of these block copolymers wherein the monovinyl-substituted aromatic compound and initiator are added in two or more increments prior to addition of the conjugated diene and the resulting diblock chains having varying styrene block links are thereafter coupled with a polyfunctional coupling agent.
As is generally the case, the properties of the resulting polymers can be varied by varying the polymerization technique. For instance, if a more flexible material is desired, a smaller amount of monovinyl-substituted aromatic component and a larger amount of conjugated diene can be utilized, but this of course results in sacrificing other properties such as hardness.